Publications

In recent years the use of alternative fuels in thermal engine power plants has gained more and more attention becoming of paramount importance to overcome the use of fuels from fossil sources and to reduce polluting emissions. The present work deals with the analysis of the response to two different gas fuels—i.e. hydrogen and a syngas from agriculture product—of a 30 kW micro gas turbine integrated with a solar field. The solar field included a thermal storage system to partially cover loading requests during night hours reducing fuel demand. Additionally a Heat Recovery Unit was included in the plant considered and the whole plant was simulated by Thermoflex® code. Thermodynamics analysis was performed on hour-to-hour basis for a given day as well as for 12 months; subsequently an evaluation of cogeneration efficiency as well as energy saving was made. The results are compared against plant performance achieved with conventional natural gas fueling. After analyzing the performance of the plant through a thermodynamic analysis the study was complemented with CFD simulations of the combustor to evaluate the combustion development and pollutant emissions formation particularly of NOx with the two fuels considered using Ansys-Fluent code and a comparison was made.

Green hydrogen is expected to play a vital role in decarbonizing the energy system in Europe. However large-scale deployment of green hydrogen has associated potential trade-offs in terms of climate and other environmental impacts. This study aims to shed light on a comprehensive sustainability assessment of this large-scale green hydrogen deployment based on the EMPIRE energy system modeling compared with other decarbonization paths. Process-based Life Cycle Assessment (LCA) is applied and connected with the output of the energy system model revealing 45% extra climate impact caused by the dedicated 50% extra renewable infrastructure to deliver green hydrogen for the demand in the sectors of industry and transport in Europe towards 2050. Whereas the analysis shows that green hydrogen eventually wins on the climate impact within four designed scenarios (with green hydrogen with blue hydrogen without green hydrogen and baseline) mainly compensated by its clean usage and renewable electricity supply. On the other hand green hydrogen has a lower performance in other environmental impacts including human toxicity ecotoxicity mineral use land use and water depletion. Furthermore a monetary valuation of Life Cycle Impact (LCI) is estimated to aggregate 13 categories of environmental impacts between different technologies. Results indicate that the total monetized LCI cost of green hydrogen production is relatively lower than that of blue hydrogen. In overview a large-scale green hydrogen deployment potentially shifts the environmental pressure from climate and fossil resource use to human health mineral resource use and ecosystem damage due to its higher material consumption of the infrastructure.

Many industrialised nations recently concentrated their focus on hydrogen as a viable option for the decarbonisation of fossil-intensive sectors including maritime transportation. A sustainable alternative to the conventional production of hydrogen based on fossil hydrocarbons is water electrolysis powered by renewable energy sources. This paper presents a detailed techno-economic optimisation model for sizing an electrolyser and a hydrogen storage embedded in a multi-domain virtual power plant to produce green hydrogen for seaborne passenger transportation. We base our numerical analysis on three years of historical data from a renewable-dominated 60/10 kV substation on the Danish island of Bornholm and on data for ferries to the mainland of Sweden. Our analysis shows that an electrolyser system serves as a valuable flexibility asset on the electrical demand side while supporting the thermal management of the district heating system and contributing to meeting the ferries hydrogen demand. With a sized electrolyser of 9.63 MW and a hydrogen storage of 1.45 t the hydrogen assets are able to take up a large share of the local excess electricity generation. The waste heat of the electrolyser delivers a significant share of 21.4% of the annual district heating demand. Moreover the substation can supply 26% of the hydrogen demand of the ferries from local resources. We further examine the sensitivity of the asset sizing towards investment costs electrolyser efficiency and hydrogen market prices.

Hydrogen is one of a handful of new low carbon solutions that will be critical for the transition to net zero. The upscaling of production and applications entails that hydrogen is likely to be stored in liquid phase (LH2) at cryogenic conditions to increase its energy density. Widespread LH2 use as an alternative fuel will require significant infrastructure upgrades to accommodate increased bulk transport storage and delivery. However current LH2 bulk storage separation distances are based on subjective expert recommendations rather than experimental observations or physical models. Experimental studies of large-scale LH2 release are challenging and costly. The existing large-scale tests are scarce and numerical studies are a viable option to investigate the existing knowledge gaps. Controlled or accidental releases of LH2 for hydrogen refueling infrastructure would result in high momentum two-phase jets or formation of liquid pools depending on release conditions. Both release scenarios lead to a flammable/explosive cloud posing a safety issue to the public.<br/>The manuscript reports exploratory study to numerically determine the safety zone resulting from cryogenic hydrogen releases related to LH2 storage and refueling using the in-house HyFOAM solver further modified for gaseous hydrogen releases at cryogenic conditions and the subsequent atmospheric dispersion and ignition within the platform of OpenFOAM V8.0. The current version of the solver neglects the flashing process by assuming that the temperature of the stored LH2 is equal to the boiling point at the atmospheric condition. Numerical simulations of dispersion and subsequent ignition of LH2 release scenarios with respect to different release orientations release rates release temperatures and weather conditions were performed. Both hydrogen concentration and temperature fields were predicted and the boundary of zones within the flammability limit was also defined. The study also considered the sensitivities of the consequences to the release orientation wind speed ambient temperature and release content etc. The effect of different barrier walls on the deflagration were also evaluated by changing the height and location.

This paper presents an energy management system (EMS) based on a novel approach using model predictive control (MPC) for the optimized operation of power sources in a hybrid charging station for electric vehicles (EVs). The hybrid charging station is composed of a photovoltaic (PV) system a battery a complete hydrogen system based on a fuel cell (FC) electrolyzer (EZ) and tank as an energy storage system (ESS) grid connection and six fast charging units all of which are connected to a common MVDC bus through Z-source converters (ZSC). The MPC-based EMS is designed to control the power flow among the energy sources of the hybrid charging station and reduce the utilization costs of the ESS and the dependency on the grid. The viability of the EMS was proved under a long-term simulation of 25 years in Simulink using real data for the sun irradiance and a European load profile for EVs. Furthermore this EMS is compared with a simpler alternative that is used as a benchmark which pursues the same objectives although using a states-based strategy. The results prove the suitability of the EMS achieving a lower utilization cost (-25.3%) a notable reduction in grid use (-60% approximately) and an improvement in efficiency.

Hydrogen is gaining importance to decarbonize the energy system and tackle the climate crisis. This exploratory study analyzes three focus groups with representatives from relevant organizations in a Northern German region that has unique beneficial characteristics for the transition to a hydrogen economy. Based upon this data (1) a category system of innovation adoption barriers for hydrogen technologies is developed (2) decision levels associated with the barriers are identified (3) detailed insights on how decision levels contribute to the adoption barriers are provided and (4) the barriers are evaluated in terms of their importance. Our analysis adds to existing literature by focusing on short-term barriers and exploring relevant decision levels and their associated adoption barriers. Our main results comprise the following: flaws in the funding system complex approval procedures lack of networks and high costs contribute to hydrogen adoption barriers. The (Sub-)State level is relevant for the uptake of the hydrogen economy. Regional entities have leeway to foster the hydrogen transition especially with respect to the distribution infrastructure. Funding policy technological suitability investment and operating costs and the availability of distribution infrastructure and technical components are highly important adoption barriers that alone can impede the transition to a hydrogen economy.

In order to reduce carbon emissions the effects of gas composition and initial turbulence on the premixed flame dynamics of hydrogen-blended natural gas were investigated. The results show that an increase in hydrogen content leads to earlier formation of flame wrinkles. When the equivalence ratio is 1 and hydrogen blending ratio is below 20% Tulip flames appear approximately 2.25 m away from the ignition point. When hydrogen blending ratio exceeds 20% Tulip flames appear approximately 1.3 m away from the ignition point and twisted Tulip flames appear approximately 2.5 m away from the ignition position. During the 0.05 m process of flame propagation downstream from ignition point flame propagation velocity increases by about 2 m/s for every 10% increase in hydrogen content. The increase in hydrogen content has the most significant impact on the flame propagation velocity during the ignition stage. The average flame propagation velocity increases with the increase of hydrogen blending ratio. The greater the initial turbulence the more obvious the stretching deformation of flame front structure. With the increase of wind speed the flame propagation velocity first increases and then decreases. At a wind speed of 3 m/s the flame propagation velocity reaches its maximum value.

The literature lacks a systematic analysis of HRS equipment and operating standards. Researchers policymakers and HRS operators could find this information relevant for planning the network's future expansion. This study is intended to address this information need by providing a comprehensive strategic overview of the regulations currently in place for the construction and maintenance of hydrogen fueling stations. A quick introduction to fundamental hydrogen precautions and hydrogen design is offered. The paper therefore provides a quick overview of hydrogen's safety to emphasize HRS standards rules and regulations. Both gaseous and liquid safety issues are detailed including possible threats and installation and operating expertise. After the safety evaluation layouts equipment and operating strategies for HRSs are presented followed by a review of in-force regulations: internationally by presenting ISO IEC and SAE standards and Europeanly by reviewing the CEN/CENELEC standards. A brief and concise analysis of Italy's HRS regulations is conducted with the goal of identifying potential insights for strategic development and more convenient technology deployment.

This study evaluates the integration of wind energy into greenhouse agriculture in the Safi region a major agricultural area in Morocco. As part of cleaner energy systems five wind turbines were analyzed to determine their performance. After performing a statistical analysis using the Weibull distribution with two parameters the results showed that the VESTAS V82- 0.9/1.65MW – 70m turbine was the most efficient. It achieved a capacity factor of 41.72% an annual energy production of 3 326.17 MWh and the ability to supply electricity to 6 960 m² of agricultural greenhouses. Environmental benefits include a significant reduction in carbon dioxide emissions. Economically the results vary with a payback period of less than 5 years for the VESTAS turbine but a longer period of 10.49 years for the Norwin – 30m turbine. To address fluctuations in wind energy caused by daily wind speed variations this innovative study explores combining wind power with hydrogen production. The results indicate that the Safi region has the potential to produce between 25 188.76 kg and 44 875.25 kg of hydrogen annually depending on the turbine used. Additionally this approach could reduce annual CO2 emissions by up to 2 606 609 kg. These findings highlight a promising innovation in cleaner energy systems to enhance agricultural sustainability through renewable energy solutions.

This paper presents an advanced Adaptive Sliding Mode Control (ASMC) strategy specifically developed for a hydrogen production system based on a Proton Exchange Membrane electrolyzer (PEM electrolyzer). This work utilized a static model of the PEM electrolyzer characterized by its V-I electrical characteristic which was approximated by a linear equation. The ASMC was designed to estimate the coefficients of this equation which are essential for designing an efficient controller. The primary objective of the proposed control strategy is to ensure the overall stability of the integrated system comprising both an interleaved buck converter (IBC) and PEM electrolyzer. The control framework aims to maintain the electrolyzer voltage at its reference value despite the unknown coefficients while ensuring equal current distribution among the three parallel legs of the IBC. The effectiveness of the proposed approach was demonstrated through numerical simulations in MATLAB-SIMULINK and was validated by the experimental results. The results showed that the proposed ASMC achieved a voltage tracking error of less than 2% and a current distribution imbalance of only 1.5%. Furthermore the controller exhibited strong robustness to parameter variations effectively handling fluctuations in the electrolyzer’s ohmic resistance (Rohm) (from ±28.75% to ±40.35%) and in the reversible voltage (Erev) (from ±28.67% to ±40.19%) highlighting its precision and reliability in real-world applications.

A city of the future will need to be eco-friendly while meeting general social and economic requirements. Hydrogen-based technologies provide solutions for initially limiting CO2 emissions with prospects indicating complete decarbonization in the future. Cities will need to adopt and integrate these technologies to avoid a gap between the development of hydrogen production and its urban application. Achievable results are analyzed by injecting hydrogen into the urban methane gas network initially in small proportions but gradually increasing over time. This paper also presents a numerical application pertaining to the city of Bucharest Romania—a metropolis with a population of 2.1 million inhabitants. Although the use of fuel cells is less advantageous for urban transport compared to electric battery-based solutions the heat generated by hydrogen-based technologies such as fuel cells can be efficiently utilized for residential heating. However storage solutions are required for residential consumption separate from that of urban transport along with advancements in electric transport using existing batteries which necessitate a detailed economic assessment. For electricity generation including cogeneration gas turbines have proven to be the most suitable solution. Based on the analyzed data the paper synthesizes the opportunities offered by hydrogen-based technologies for a city of the future.

H2 geo-storage has been suggested as a key technology with which large quantities of H2 can be stored and withdrawn again rapidly. One option which is currently explored is H2 storage in sedimentary geologic for mations which are geographically widespread and potentially provide large storage space. The mechanism which keeps the buoyant H2 in the subsurface is structural trapping where a caprock prevents the H2 from rising by capillary forces. It is therefore important to assess how much H2 can be stored via structural trapping under given geo-thermal conditions. This structural trapping capacity is thus assessed here and it is demonstrated that an optimum storage depth for H2 exists at a depth of 1100 m at which a maximum amount of H2 can be stored. This work therefore aids in the industrial-scale implementation of a hydrogen economy.

This second edition of the European Maritime Transport Environmental Report (EMTER 2025) examines the progress made towards achieving Europe′s decarbonisation targets and environmental goals for the maritime sector while indicating the most important trends key challenges and opportunities. The objective was to update the indicators developed for the first report analyse new datasets and fill existing gaps to provide a data and knowledge-based assessment of the maritime transport sector′s transition to sustainability.

In this study Distribution of Relaxation Times (DRT) was successfully demonstrated in the analysis of the impedance spectra of High-Temperature Polymer Electrolyte Membrane Fuel Cells (HT-PEMFC) doped with phosphoric acid. Electrochemical impedance spectroscopy (EIS) was performed and the quality of the recorded spectra was verified by Kramers-Kronig relations. DRT was then applied to the measured spectra and polarization losses were separated on the basis of their typical time constants. The main features of the distribution function were assigned to the cell’s polarization processes by selecting appropriate experimental conditions. DRT can be used to identify individual internal HT-PEMFC fuel cell phenomena without any a-priori knowledge about the physics of the system. This method has the potential to further improve EIS spectra interpretation with either equivalent circuits or physical models.

The production of hydrogen from renewable sources could play a significant role in supporting the transition toward a decarbonized energy system. This study has involved investigating optimization strategies − mixedinteger linear programming (MILP) a hybrid particle swarm optimization (PSO)-MILP framework and PSO combined with a rule-based energy management strategy (EMS) − applied to a power-to-hydrogen system for industrial applications. The analysis evaluates the levelized cost of hydrogen production (LCOH) carbon emissions and the impact of key factors such as battery degradation electrolyzer efficiency real-time pricing and hydrogen load management. The obtained results indicated that the MILP-based models achieved moderate LCOH values (10.1–10.7 €/kg) but incurred higher CO2 emissions (20.2–24.6 kt/y). Instead the PSO model combined with the rule-based EMS lowered emissions to 14.3 kt/y (a 27–45% reduction) albeit with a higher LCOH (11.6 €/kg). The hybrid PSO-MILP models struck a balance achieving LCOH values of between 9.2 and 9.7 €/kg with CO2 emissions of 19.7–20.3 kt/y as they benefited from the integration of piecewise affine linearization for modeling electrolyzer efficiency and battery degradation. In terms of computational efforts the MILP-based models required more than 48 h to converge while the PSO-MILP models completed within 27–35 h and the PSO model with rule-based EMS achieved results in 1.5 h. These findings offer guidance that can be used to select the most suitable optimization method on the basis of the desired performance targets resource constraints and computational complexity thereby contributing to the design of more sustainable energy systems.

Different photoelectrochemical (PEC) artificial-leaf systems have been proposed for green hydrogen production. However their sustainability is not well understood in comparison to conventional hydrogen technologies. To fill this gap this study estimates cradle-to-grave life cycle environmental impacts and costs of PEC hydrogen production in different provinces in China using diverse tandem solar cells: Ge/GaAs/GaInP (Ge-PEC) GaAs/ GaInAs/GaInP (GaAs-PEC) and perovskite/silicon (P-PEC). These systems are benchmarked against conventional hydrogen production technologies − coal gasification (CG) and steam methane reforming (SMR) − across 18 environmental categories life cycle costs and levelised cost of hydrogen (LCOH). P-PEC emerges as the best options with 36–95 % lower impacts than Ge-PEC and GaAs-PEC across the categories including the climate change impact (0.38–0.52 t CO2 eq./t H2) which is 77–79 % lower. Economically P-PEC shows 81–84 % lower LCOH (2.51–3.81 k$/t). Compared to SMR and CG P-PEC reduces the impacts by 23–98 % saving 3.67–38.5 Mt of CO2 eq./yr. While its LCOH is 5 % higher than that of conventional hydrogen it could be economically competitive with both SMR and CG at 10 % higher solar-to-hydrogen efficiency and 25 % lower operating costs. In contrast Ge-PEC and GaAs-PEC while achieving much lower (81–91 %) climate change and some other impacts than the conventional technologies face significant economic challenges. Their LCOH (21.51–32.82 k$/t for Ge-PEC and 16.96–25.89 k$/t for GaAs-PEC) is 7–9 times higher than that of the conventional hydrogen due to the high solar cell costs. Therefore despite their environmental benefits these technologies require substantial cost reductions to become economically viable.

Hydrogen valleys are envisaged (imagined) integrated industrial systems where hydrogen is produced stored and utilized. Here we show how hydrogen valleys as sociotechnical imaginaries are differentiated in terms of their specific configurations but homogenous in terms of reflecting the interests of large industrial fossil fuel suppliers and consumers. This path dependence is anticipated in sociotechnical transitions theory which emphasises the power of incumbents with vested interests to maintain basic templates or regimes of production and consumption. The simultaneously heterogeneous and homogenous nature of hydrogen valley imaginaries can be thought of as a form of glocalisation for which we draw on Roudometof's theory of glocalisation as involving the local refraction of diffusing global tendencies. To illustrate this we compare two hydrogen valleys one in the north of the Netherlands and one in southern Spain. In the north Netherlands the hydrogen valley imaginary comprises use of offshore windpower to electrolyse hydrogen for transport fuel and as feedstock to heavy industry in proximate regions including northern Germany and Belgium. This is consistent with existing gas distribution networks connecting industrial consumers. In the southern Spanish case the imaginary positions Spain as a major exporter of green hydrogen to the rest of Europe via onshore renewable electrolysis with export including via ocean tankers and chemical refining in existing infrastructure in Rotterdam. Overall the study explores empirically theoretically-informed themes concerning the interrelationship of mutually supportive local and global imaginaries – hence our term glocalised imaginaries.

Hydrogen economy is spreading across the maritime sector in response to increasingly stringent regulations for shipping emissions. The challenging on-board hydrogen logistics are often mitigated with hydrogen carriers such as methanol. Research on methanol reforming to hydrogen for fuel cell feed is conducted mostly in steady state overlooking dynamic reactor operation and its effects on the power production system. Forced reactor operations induce fluctuations of CO content in the reformate potentially harmful to the PEM fuel cell and drops in methanol conversion causing inefficient operation. In present research simulations with a physical 2D unsteady model of a packed bed methanol steam reforming reactor resulted in methanol conversion drop durations of up to a minute. Additionally temporary increases of CO content up to 112% were observed. Throughput ramp ups most notably impact the conversion while ramp downs negatively affect selectivity. The investigation on reactor geometry concludes that larger tube diameters increase transient time and CO spikes while they decrease with reactor length. Amplified unsteady effects are also observed with larger changes in input process variables. The results imply that heat transfer rate to the reactor are most often the detrimental factor for transient effects and durations in practice. Following this work inclusion of realistic heating methods is recommended instead of uniform tube temperatures used in present simulations. Heating system characteristics are necessary for realistic evaluation of the methanol reformer constraint on fuel cell feed demand in fully integrated systems.

Hydrogen tanks (HT) with different connection modes are an integral part of the shipborne hydrogen fuel cell system. To ensure the safe and reliable operation of the shipborne multi-tank cascade system this study innovatively develops 3D models of four different connection modes for the shipborne multi-tank cascade system namely Type-22 Type-211 Type-121 and Type-112. Through computational fluid dynamics (CFD) numerical simulation the variations in parameters of different multi-tank cascade systems during the hydrogen storage process are analyzed. The results indicate that the maximum temperature of Type-112 is 271.107K which is 2.220% 4.779% and 3.993% lower than that of Type-22 Type-211 and Type-121 respectively and thus the optimal parameters such as the initial temperature in the tank and pre-cooling temperature are derived. Type-112's maximum temperature is reduced by 14.02% and 16.66% compared to systems connected solely in series or in parallel. The study identifies the optimal structure and reasonable hydrogen storage parameters effectively reducing heat generation during the refueling process while optimizing space utilization thereby strongly ensuring the stability of hydrogen storage and opening up new avenues for addressing related hydrogen storage issues in the future.

Mobility has been a prominent target for proponents of the hydrogen economy. Given the complexities involved in the mobility value chain actors hoping to participate in this nascent market must overcome a range of challenges relating to the availability of vehicles the co-procurement of supporting infrastructure a favourable regulatory environment and a supportive community among others. In this paper we present a state-of-play account of the nascent hydrogen mobility market in Victoria Australia drawing on data from a workshop (N ¼ 15) and follow-up interviews (n ¼ 10). We interpret findings through a socio-technical framework to understand the ways in which fuel cell electric vehicles (FCEVs)dand hydrogen technologies more generallydare conceptualised by different stakeholder groups and how these conceptualisations mediate engagement in this unfolding market. Findings reveal prevailing efforts to make sense of the FCEV market during a period of considerable institutional ambiguity. Discourses embed particular worldviews of FCEV technologies themselves in addition to the envisioned roles the resultant products and services will play in broader environmental and energy transition narratives. Efforts to bring together stakeholders representing different areas of the FCEV market should be seen as important enablers of success for market participants.

This paper aims to present an overview of the current state of hydrogen storage methods and materials assess the potential benefits and challenges of various storage techniques and outline future research directions towards achieving effective economical safe and scalable storage solutions. Hydrogen is recognized as a clean secure and costeffective green energy carrier with zero emissions at the point of use offering significant contributions to reaching carbon neutrality goals by 2050. Hydrogen as an energy vector bridges the gap between fossil fuels which produce greenhouse gas emissions global climate change and negatively impact health and renewable energy sources which are often intermittent and lack sustainability. However widespread acceptance of hydrogen as a fuel source is hindered by storage challenges. Crucially the development of compact lightweight safe and cost-effective storage solutions is vital for realizing a hydrogen economy. Various storage methods including compressed gas liquefied hydrogen cryocompressed storage underground storage and solid-state storage (material-based) each present unique advantages and challenges. Literature suggests that compressed hydrogen storage holds promise for mobile applications. However further optimization is desired to resolve concerns such as low volumetric density safety worries and cost. Cryo-compressed hydrogen storage also is seen as optimal for storing hydrogen onboard and offers notable benefits for storage due to its combination of benefits from compressed gas and liquefied hydrogen storage by tackling issues related to slow refueling boil-off and high energy consumption. Material-based storage methods offer advantages in terms of energy densities safety and weight reduction but challenges remain in achieving optimal stability and capacities. Both physical and material-based storage approaches are being researched in parallel to meet diverse hydrogen application needs. Currently no single storage method is universally efficient robust and economical for every sector especially for transportation to use hydrogen as a fuel with each method having its own advantages and limitations. Moreover future research should focus on developing novel materials and engineering approaches in order to overcome existing limitations provide higher energy density than compressed hydrogen and cryo-compressed hydrogen storage at 70 MPa enhance costeffectiveness and accelerate the deployment of hydrogen as a clean energy vector.

This study investigates the effect of Oxygen-Enriched Combustion on hydrogen-enriched natural gas (H2 -NG) fuel mixtures at a semi-industrial scale (up to 60 kW). The analysis focuses on flame structure temperature distribu tion in the furnace NOx emissions and potential fuel savings. A multi-fuel multi-oxidizer jet burner was used to compare two oxygen enrichment configurations: premixed with air (PM) and air-pure O2 (AO) independent feed. The O2 -enriched flames remained stable across the entire fuel range. OH* chemiluminescence imaging for the H2 -NG fuel mixture delivering 50 concentration kW revealed that higher O2 increases the OH* intensity narrows and elongates the flame transitions from buoyancy- to momentum-driven shape and relocates the reaction zone. At 50 % oxygen enrichment level (OEL) flame shape OH* intensity and temperature profiles resembled pure O combustion. Up to 29 % OEL furnace temperature profiles were similar to those 2 of air-fuel combustion. The power required to maintain 1300 ± 25 ◦C at the reference position decreases with O2 enrichment. Higher OELs resulted in a sharp increase in NOx emissions. The effect of hydrogen enrichment on NOx levels was significantly less pronounced than that of oxygen enrichment. The rise in NOx emissions correlates with increased OH* in tensities. For a 50 % H2 2 blend increasing the O concentration in the oxidizer from 21 % to 50 % resulted in a 27 % reduction in flue gas heat losses. Utilizing O2 co-produced with H2 could be strategic for reducing fuel consumption facilitating the adoption of hydrogen-based energy systems.

This report is an output of the Clean Energy Technology Observatory (CETO) and is an update of the “Water electrolysis and hydrogen in the European Union” 2023 CETO report. CETO’s objective is to provide an evidencebased analysis feeding the policy making process and hence increasing the effectiveness of R&I policies for clean energy technologies and solutions. It monitors EU research and innovation activities on clean energy technologies needed for the delivery of the European Green Deal; and assesses the competitiveness of the EU clean energy sector and its positioning in the global energy market. CETO is being implemented by the Joint Research Centre for DG Research and Innovation Energy in coordination with DG Energy.

To achieve energy transition hydrogen and carboxylic acids have attracted much attention due to their cleanliness and renewability. Anaerobic fermentation technology is an effective combination of waste biomass resource utilization and renewable energy development. Therefore the utilization of anaerobic fermentation technology is expected to achieve efficient co-production of hydrogen and carboxylic acids. However this process is fundamentally affected by gas–liquid mass transfer kinetics bubble behaviors and system partial pressure. Moreover the related studies are few and unfocused and no systematic research has been developed yet. This review systematically summarizes and discusses the basic mathematical models used for gas–liquid mass transfer kinetics the relationship between gas solubility and mass transfer and the liquid-phase product composition. The review analyzes the roles of the headspace gas composition and partial pressure of the reaction system in regulating co-production. Additionally we discuss strategies to optimize the metabolic pathways by modulating the gas composition and partial pressure. Finally the feasibility of and prospects for the realization of hydrogen and carboxylic acid co-production in anaerobic fermentation systems are outlined. By exploring information related to gas mass transfer and system pressure this review will surely provide an important reference for promoting cleaner production of sustainable energy.

To achieve deep decarbonization in the transportation sector this study employs life cycle assessment (LCA) and the GREET model to construct baseline and low-carbon scenarios. It simulates the evolution of emissions and energy consumption within Inner Mongolia’s public transportation energy system (including diesel buses (DBs) electric buses (EBs) and hydrogen fuel cell buses (HFCBs)) from 2022 to 2035 while exploring synergistic pathways for its low-carbon transition. Results reveal that under the baseline scenario reliance on industrial by-product hydrogen causes fuel cell bus emissions to increase by 3.64% in 2025 compared to 2022 with system energy savings below 10% and decarbonization potential will be constrained by scale limitations and storage/transportation losses in cold regions. Under the low-carbon scenario deep grid decarbonization vehicle structure optimization and green hydrogen integration reduced system emissions and energy consumption by 66.86% and 40.44% respectively compared to 2022. The study identifies a 15% green hydrogen penetration rate as the critical threshold for resource misallocation and confirms grid decarbonization as the top-priority policy tool yielding marginal benefits 1.43 times greater than standalone hydrogen policies. This study underscores the importance of multipolicy coordination and ‘technology-supply chain’ synergy particularly highlighting the critical threshold of green hydrogen penetration and the primacy of grid decarbonization offering insights for similar coal-dominated cold-region transportation energy transitions.